Hierarchical Micro-Nano Surface Topography Promotes Long-Term Maintenance of Undifferentiated Mouse Embryonic Stem Cells.

Understanding of stem cell-surface interactions and, in particular, long-term maintenance of stem cell pluripotency on well-defined synthetic surfaces is crucial for fundamental research and biomedical applications of stem cells. Here, we show that synthetic surfaces possessing hierarchical micro-nano roughness (MN-surfaces) promote long-term self-renewal (>3 weeks) of mouse embryonic stem cells (mESCs) as monitored by the expression levels of the pluripotency markers octamer-binding transcription factor 4 (Oct4), Nanog, and alkaline phosphatase. On the contrary, culturing of mESCs on either smooth (S-) or nanorough polymer surfaces (N-surfaces) leads to their fast differentiation. Moreover, we show that regular passaging of mESCs on the hierarchical MN-polymer surface leads to an increased homogeneity and percentage of Oct4-positive stem cell colonies as compared to mESCs grown on fibroblast feeder cells. Immunostaining revealed the absence of focal adhesion markers on all polymer substrates studied. However, only the MN-surfaces elicited the formation of actin-positive cell protrusions, indicating an alternative anchorage mechanism involved in the maintenance of mESC stemness.

Micropatterned superhydrophobic structures for the simultaneous culture of multiple cell types and the study of cell-cell communication.

The ability to control spatial arrangement and geometry of different cell types while keeping them separated and in close proximity for a long time is crucial to mimic and study variety of biological processes in vitro. Although the existing cell patterning technologies allow co-culturing of different cell types, they are usually limited to relatively simple geometry. The methods used for obtaining complex geometries are usually applicable for patterning only one or two cell types. Here we introduce a convenient method for creating patterns of multiple (up to twenty) different cell types on one substrate. The method virtually allows any complexity of cell pattern geometry. Cell positioning on the substrate is realized by a parallel formation of multiple cell-containing microreservoirs confined to the geometry of highly hydrophilic regions surrounded by superhydrophobic borders built-in a fine nanoporous polymer film. As a case study we showed the cross-talk between two cell populations via Wnt signaling molecules propagation during co-culture in a mutual culture medium.